Fractography of fracture in CFRP under compressive load

Abstract The mechanical properties of the fiber/resin interphase affect both the macroscopic mechanical properties of the composite material and those of the fiber and resin. Interfacial properties are therefore very important for mechanical design. Carbon-fiber-reinforced plastics (CFRP) commonly have a laminated structure, and the fracture mechanism in CFRP is a complex problem. Fractography is well known to be a useful technique for elucidation of the fracture process. In this paper, axial compressive tests were carried out on unidirectional laminated CFRP. The carbon fibers used in this report were of the PAN-based high-strength type and the pitch-based high-modulus type, and were subjected to various degrees of surface treatment. In this paper the degree of electrical charge is revealed. The effect of surface treatment on the fracture process in these CFRP was examined by scanning electron microscope. As a conclusion, flexural fracture of the reinforcements is mainly caused by delamination of the fiber/resin interphase, and improvement of the interphase by surface treatment could control the flexural fracture of reinforcements.